Tires are an integral part of mountain bike riding, and here are a few tips, pointers, and generalized information about them for our riders
*A tire's performance is measured by it's ability to convert the energy produced by the rider into forward momentum. This performance is also related to the tire's size, design, casing design, rubber compounds and tread patterns. For dirt and loose surfaces, width, tread and rubber compound play a major role in generating traction.
*There are 2 types of flat tires - pinch flats and puncture flats. Pinch flats usually occur while riding at high speed over an obstacle, and the inner tube is pinched between the edge of the rim and the tire. This usually leaves two sets of punctures - a double hole- that look like a "snakebite"
when you examine the tube. Puncture flats and cuts come from nails, rocks, glass, thorns, rought terrain, cacti, or other sharp objects you may encounter. Usually these occur on the tread side of the tire, and you may find the agent causing the puncture to still be embedded in the tire. You can avoid punctures by using tires with a thicker tread, or those with reinforcement under the tread. Casings with a higher thread count (more than 100/inch) also tend to be more puncture resistance. Downhill tires usually are quite resistant to most flats verses cross country tires, but they weigh more.
*Rubber compound of your tire can also make a difference in feel and traction. Harder compounds offer high mileage and extended wear - but softer compounds have loads of grip, but may wear out faster. Make sure that your tires are not more than a few seasons old - even if you do not ride them they will dry out with age and may require replacement.
*The casing design (measured in threads per inch) also can tell you about the characteristics of the tire. Usually the higher the thread count, the more resistant it will be to impact damage from rocks and obstacles, and the tire will feel "beefier" when you handle it while mounting.
*Mountain bikes use 26 inch tires most of the time. Smaller or kids bikes may have 24 inch tires, and some specialist mountain bikes or singlespeed bikes may use 29 inch tires!! Keep in mind that 26 inches does not necessarily refer to the diameter of the rim nor that of the tire!! It is just the most common size of tire, on almost every bike. Section widths of the tire are also expressed in inches, so a 26X2.1 tire is 2.1 inches wide.
*Some tires are direction specific, so that they should be mounted with the arrow on the side wall facing forward - the direction the tire will roll. Also, some are designed specifically for the use as either a front tire or a rear tire. Most tires, however, can be used front or rear and you can put them on either rim.
*Punctures can be avoided by getting heavier tires with higher tread design, getting a higher casing number, using a tire liner between the outside of your tube and the inner wall of the tire, using a "thornproof tube" that is thicker on the outside wall, or using a self healing slime tube. Repeated punctures can be caused by failure to remove the original cause (i.e. thorn) that caused your flat to begin with. Search visually and also feel the inside of your tire with your fingertips to feel for embedded agents - sometimes they end up stuck in the tire and will cause repeated flats.
*Width of your tire will depend on the capacity of what size will fit in-between the forks for your front tire, and the chainstay for the rear tire. Sometimes a rear tire too wide will also hit the front derailleur, in addition to rubbing the frame. Most tires come in these popular sizes 26X1.75 26X1.9 26X2.1 26X2.2. The larger sizes used for extra durability or downhill riding are usually 26X2.3, 26X2.4, or 26X2.6. A wider tire will weigh more, and have more rolling resistance, but have better traction and durability.
*Your tire will either have a KEVLAR side bead or a WIRE side bead. Kevlar tires are more popular, are more flexible, and come folded up when you buy them, as they are foldable. Wire tires must not be folded and they are kept in the shape as they are on the bike. These days, most tires have a kevlar side bead...
*Ride with a consistent tire pressure and check before every ride. Alter it based on conditions and terrain if necessary.
*Use a tire pressure gauge, or pump with a gauge (Topeak Joe Blow is what I use) and check your pressure often.
*Always pump your tires up before a ride, because they always seem to lose a few psi's after a few days.
*Make sure you know if your tire has a presta valve (skinny) or Schrader valve (fat like a car). The presta valve must be loosened counter clockwise before inflating, unlike the schrader that you can just pump up directly.
*Ride with between 32-36psi hardtail, 34-36psi front suspension, and 40-50psi full suspension. These can change depending upon rider weight, conditions, and preferences. Usually I keep the same pressure in the front and the rear.
*A higher pressure means less shock absorption and less rolling resistance. A lower pressure allows for more shock absoption, but increases resistance slightly. Also, with a lower tire pressure you run a greater risk of pinch flates, and the possibility of bending or damaging your rim on big hits.
*Always carry a pump and patch kit on the trail, or make sure your buddy has one.